Positive bias temperature instability in MOSFETs

The positive bias temperature instability (PBTI) of submicron MOSFETs has been investigated. It is found that the PBTI can be as large as the well-known negative bias temperature instability (NBTI). While the NBTI includes both Interface state generation and positive charge formation in the gate oxide, the PBTI only exists in the form of donor-like interface state generation. These donor-like interface states are localized symmetrically near the source and drain junctions and are negligible in the middle of the channel. Their dependence on the stressing electrical field strength and temperature is investigated and an activation energy of 1.23 eV is extracted. The PBTI creation follows the first order kinetics and the final saturation level is fixed by the number of defects available in the device. The experimental results show that the water- and boron-related species are two necessary reactants of the electrochemical reaction leading to the PBTI. Some speculation on the PBTI formation process is included.

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